The oxidative dyeing of hair can lead to damage to the keratin fiber due to the aggressive agents. In particular, the natural hydrophobicity of the keratinic fiber is reduced since the coloring agents first have to penetrate the hair in order to develop their effect. However, the water-repellent effect is, on the one hand, a natural protection of the hair; on the other hand, desirable parameters such as gloss, suppleness, grip and “springing” of the hair are closely linked to it.
In order to overcome these disadvantages, so-called pretreatment agents are on the market which are intended to protect the hair from the aggressive influence. However, these often damage the hair or impair the success of the subsequent lightening or dyeing of the hair. In particular, the washing fastness of the dyeing may be impaired by the pretreatment agent. Numerous post-treatment agents are also known for the purpose of repairing the hair damage caused by the oxidative dyeing treatment. However, all of these methods require a multi-stage application method, either an application of a further hair treatment agent before or after the dyeing. This is often perceived as cumbersome by the consumer, since even the oxidative dyeing treatment itself, with several working steps and an exposure time of up to 60 minutes, requires much effort.
The object of the present disclosure was to provide an agent and a method for oxidative hair dyeing with a hair-protecting treatment which overcomes the mentioned disadvantages without adversely affecting the color result of the oxidative dyeing treatment. In particular, a coloring agent and a method are provided in which the hair is not burdened and as little hair damage as possible occurs. Furthermore, the achieved hair protection should consume as little time as possible and, if possible, occur together with the dyeing step itself.
The use of dicarboxylic acids such as succinic acid in hair care is state of the art. These are widely used in shampoos and in particular in conditioners in order to develop care effects there. Thus, patent application WO 2005/115314A1 discloses a method for the restructuring of keratin fibers in which the keratin fibers are brought into contact with cystine and with at least one dicarboxylic acid having 2 to 10 carbon atoms, wherein preferred dicarboxylic acids are selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, maleic acid, fumaric acid and sorbic acid and succinic acid is particularly preferred. The patent application DE 10051774 A1 describes the use of short-chain carboxylic acids with a molecular weight below 750 g/mol in cosmetic agents as an active ingredient for the restructuring of keratin fibers. Patent application EP1174112A discloses hair treatment agents which, in addition to an organic acid, contain an organic solvent, a cationic surfactant and a higher alcohol as further mandatory constituents, and which serve to repair pores in hair.
Recently, agents have also been offered in the market to which dyeing compositions are to be admixed and contain dicarboxylic acids for the purpose of fiber protection. In the case of the compositions mentioned, there is no application of a further hair treatment agent before or after the dyeing, however, the agent must be mixed with the actual coloring agent before application, which also means a further work step and is considered cumbersome by the consumer.